A. Field of the Invention
The present invention relates generally to wireless messaging systems and, more particularly, to a wireless messaging system providing the capability to receive data information, including real-time weather and traffic alerts as well as personal messages, transmitted within a commercial broadcast band via a computer system.
B. Background of the Invention
1. FM Subcarrier Technology
FM subcarrier technology has been used in a number of applications, using a variety of analog and digital communication schemes. For example, Muzak, the familiar xe2x80x9celevatorxe2x80x9d music piped into physicians"" offices, elevators and the like, uses a double side band AM modulation of a 67 KHz subcarrier to carry subscription music.
In another FM subcarrier application, known in Europe as the Radio Data System (RDS) and in the United States as the Radio Broadcast Data Service (RBDS), a 57 KHz subcarrier is modulated using bipolar phase shift keying to carry a low speed (1187.5 bps) digital data signal. This technique incorporates a unique block and bit synchronization method as well as a simple linear block encoding for error detection and correction. RDS is a very robust digital subcarrier communication scheme because of its long baud interval (xcx9c1 ms), low subcarrier frequency, and narrow bandwidth. This technology was originally invented and perfected by the Swedish Telecommunications Office and later extended in the rest of Europe. It has been adopted as an international standard and incorporates specification of the physical layer (the modulation and FM interface), the data link layer (error correction coding), and a network layer for service delivery. The channel modulation efficiency of RDS is about 0.3 bps/Hz.
Because of the low data rate of RDS, another format known as the Data Radio Channel (DARC) was invented by NHK in Japan to support a higher data rate FM subcarrier service. DARC is encapsulated into international standards (cf., EIA-794) as having four modes of operation at the physical level. The differences among these four modes involve the amount of error correction coding (ECC) overhead applied to the data transmission. At the physical layer, DARC is 16K bits per second minimum-shift keyed modulation of a 76K Hz subcarrier tone. DARC specifies all of the first four layers of the communications methodology: Physical, Data Link, Network, and the Transport layers.
Of the four modes of operation, the Frame B mode of DARC provides the best channel coding and error correction ability at the cost of reduced data payload rate. The net data rate, after application of layer 2 and layer 3 overhead, is 6,210 bits per second (bps). DARC offers a channel bit rate efficiency of about 0.66 bps/Hz, the typical value for a minimum-shift keyed modulation. This level of efficiency drops considerably after application of ECC.
Because of DARC""s relatively high data rate, it has achieved use worldwide. Several IC manufacturers now deliver highly integrated decoders for receiver/demodulation design. Among the countries actively utilizing DARC systems are Sweden, Germany, Austria, France, Hungary, Japan, and the USA.
Offering comparable performance to DARC is the Subcarrier Traffic Information Channel (STIC) developed by the Mitre Corporation under finding from the Department of Transportation, Federal Highway Administration. This digital system uses a differentially encoded, quadrature phase-shift keyed modulation of either a 72.2K Hz of a 87.4K Hz subcarrier tone to deliver a 18,050 or 21,850 bps raw data rate. STIC also has a US standard (EIA-795) but is little known beyond the USA and has seen virtually no commercial use. Like the above systems, the STIC standard addresses layers 1 through 4 of the communications hierarchy. STIC is notable because it applies modern modem technology to a FM subcarrier system by using efficient convolutional coding, code concatenation and interleaving at the bit level to address channel impairments. The overall efficiency of STIC is on the order of 1.15 bps/Hz at the channel bit rate and a net of about 0.6 bps/Hz. Neither figure represents a very aggressive design. However, STIC was reported to be slightly superior to DARC in terms of overall performance in tests conducted in the USA by the Electronics Industry Association (EIA).
Several other xe2x80x9chigh-speedxe2x80x9d subcarrier technologies have been developed over the past 10 years in the United States. Some of the more notable attempts are Seiko""s 19K baud (8K bps nominal), SCA Data System""s 32K bps proprietary system, Data Broadcasting Corporation""s 19.2K bps FSK system, and Command Audio""s proprietary DQPSK system, which is very similar to STIC in concept and structure. Command Audio has a portable subscriber unit, manufactured under license by Thompson Electronics, RCA Consumer Products Division, in commercial trials in Denver and Phoenix at the current time. Again, this system barely reaches a 2 bps/Hz efficiency. By contrast, telephone modem technology operates at 7 bps/Hz almost universally throughout the world, illustrating the difficulty of the propagation environment to which FM subcarrier systems are subjected and the rather low efficiency of the current FM subcarrier systems.
2. Computer Systems
Computer systems and, more particularly, portable laptop computers, palm-top computers, and personal digital assistants (xe2x80x9cPDAsxe2x80x9d) continue to grow in popularity. As reliance upon such computer systems to accumulate and organize information as well as to facilitate communication continues to increase, users will keep trying to take fall advantage of the portability of their computer systems, expanding their use beyond the home and/or office.
Traditionally, a computer system required a modem or Ethernet adapter in combination with a hardwired communication link to receive information and/or to communicate with other computers. Today, wireless communications, such as communications in the cellular band, may be employed to transmit messages among remote computers without the restrictions on portability imposed by the hardwired communication link. As a result, users theoretically can utilize their computers to gather real-time information during the day simply by maintaining a connection to a communication network.
The use of existing wireless communication networks, however, suffers from a significant disadvantage: cost. Air time in the cellular band generally is very expensive. As a result, leaving one""s computer connected to the existing wireless communication networks for extended periods of time generally would not economically feasible for the average user. The user instead must carefully balance the trade-off between the expense of cellular air-time and his need for updated, real-time information.
In view of the foregoing, it is believed that a need exists for wireless communications that overcome the aforementioned obstacles and deficiencies of currently available wireless communication systems.
The present invention is directed to a wireless messaging system providing the capability to receive transmitted data information, including incoming personal messages and/or real-time information regarding news, sports scores, weather conditions, and/or traffic conditions, transmitted within a commercial broadcast band. Through the use of the present invention, a user may be able to receive e-mails and/or real-time information virtually anywhere and at any time via his computer system. The present invention thereby provides the advantage of permitting remote reception of transmitted data information without incurring the expense associated with cellular transmissions.
A radio unit in accordance with the present invention may comprise an integrated antenna system, a first radio receiver, and an interface system for removably connecting the radio unit to a computer system. The integrated antenna system may include a ferrite core, a first set of windings, and a second set of windings. The ferrite core may have a circumference, a first region, and a second region, preferably opposite the first region. To reduce the capacitance between the windings, the first set of windings preferably are wound substantially in a first direction about the circumference of the first region; whereas, the second set of windings preferably are coupled with the ferrite core by being wound substantially in a second direction about the circumference of the second region. The first direction preferably is opposite the second direction. The first set of windings may be coupled with the second set of windings substantially at a junction between the first region and the second region.
The first radio receiver may be coupled with the integrated antenna system and preferably is capable, substantially via the integrated antenna system, of receiving transmitted data information. The first radio receiver also may be coupled with the interface system and preferably is capable of communicating with the interface system. Upon receiving transmitted data information, the first radio receiver may communicate the transmitted data information to a data memory system coupled with the first radio receiver and/or to the computer system. When the radio unit is connected to the computer system substantially via the interface system, the first radio receiver preferably communicates the transmitted data information to the computer system. The computer system then may retain the transmitted data information and/or may present, for example, visually substantially via a display, the transmitted data information either in its entirety or in part according to a preselected presentation criteria.
In a second preferred embodiment, the radio unit may include a second radio receiver for receiving transmitted audio information, such as music, new reports, and/or talk-radio from a commercial radio station, and an audio system. The second radio receiver may be coupled with the integrated antenna system, and the second radio receiver preferably is capable of receiving the transmitted audio information substantially via the integrated antenna system. The second radio receiver also may be coupled with, and capable of communicating with, the interface system. Further, the second radio receiver may be coupled with the audio system, which may selectively audibly present the transmitted audio information.
It will be appreciated that a radio unit in accordance with the present invention may permit a user to receive data information, such as personal messages and/or real-time information, that is transmitted within a commercial broadcast band, thereby avoiding incurring the expense associated with cellular communications. The radio unit may also allow the user to listen to, for example, his favorite radio station while receiving transmitted data information through the use of the second radio receiver. Further, since the transmission frequency of the radio station may differ from the transmission frequency of the transmitted data information, a user of a radio unit with a single radio receiver may be unable to receive the transmitted data information upon tuning the single radio receiver to receive the radio station, and vice versa.